Computed Columns – SQL Server

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Computed columns it self does not contain any data, but shows value based on expression (given formula). Its very simple to add a computed columns in SQL Server you can either add them through DDL query or through SSMS GUI.

  • Computed columns actually are virtual columns
  • Are not physically stored in the table unless the column is marked PERSISTED.
  • If NOT PERSISTED: Values for computed columns are recalculated every time they are referenced in a query.
  • If PERSISTED: Values of computed column are updated when any columns that are part of their calculation change.
  • By marking a computed column as PERSISTED, we can create an index on a computed column.
  • Computed columns used as CHECK, FOREIGN KEY, or NOT NULL constraints must be marked PERSISTED.

Please go through following video tutorial for better understanding.

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